1. Field of the Invention
The present invention relates to an electric power steering system and a method for checking an initial driving thereof, and more particularly, an electric power steering system and a method for checking an initial driving thereof, in which no additional redischarging and charging time is required by simultaneously determining a freezing of a safety switch and/or a safety switch off of a sub MCU, which monitors a state of a main MCU, thereby shortening initial driving time of the electric power steering system.
2. Description of the Related Art
Much research has been conducted on a steering system that can arbitrarily change a driving direction of a vehicle as a driver intends.
As such a steering system, there is a hydraulic power steering (HPS) system using a hydraulic pressure of a hydraulic pump. An electric power steering (EPS) system using an electric motor has been widely used since 1990.
In the HPS system, a hydraulic pump serving as a power source to assist power is driven by an engine and always consumes energy, regardless of rotation of a steering wheel. On the other hand, in the EPS system, when a steering wheel rotates to generate a torque, a motor driven by electric energy supplies steering auxiliary power. Therefore, as compared with the HPS system, the EPS system can improve energy efficiency.
In addition, the EPS system appropriately changes a handle steering force through electronic control according to a driving speed of a vehicle. For example, the EPS system makes the steering force light during parking or low-speed driving, and makes the steering force heavy during high-speed driving, contributing to stability in high-speed driving.
In the conventional EPS system, a main MCU applies an on driving signal to a safety switch so as to check a safety switch off of a sub MCU which monitors a state of the main MCU. Then, when disabling a safety switch driving signal of the sub MCU, additional redischarging and charging time are required after the check. As a result, the initial driving time of the EPS system is lengthened. Accordingly, the conventional EPS system has difficulty in satisfying initial driving requirements required by companies.
In addition, in the conventional EPS system, when the safety switch is switched on to connect a motor and a power supply, a potential difference occurs between front and rear stages of the safety switch. Thus, the durability of the safety switch may be degraded, and peripheral circuits may be burnt by sparks.